1. Field of the Invention
This invention relates to a digital information signal recording apparatus and more particularly to a digital information signal recording apparatus which has a plurality of recording modes.
2. Description f the Related Art
A digital signal is restorable perfectly back to its original state if the S/N ratio thereof is above a certain given level. The signals of this kind are, therefore, considered to be advantageous for high quality recording and reproduction. For example, digital video recording is being performed by recording on a magnetic tape, a magnetic disc or an optical disc a digital video signal which is obtained through a digital pulse modulating process. In the case of a digital VTR for recording a video signal on a magnetic tape, the VTR is arranged to record a digital video signal at a track pitch at which the lowest allowable S/N ratio is obtainable. Since the track pitch cannot be allowed to be narrower than this, the VTR of this kind is arranged to cut down the amount of digital data (band compression) for an operation in the long-time recording mode that is practiced at present with the VTRs of the analog recording/reproducing type.
The technique for digital recording and reproduction and for a band compressing process has recently made a salient advancement. The digital VTR is capable of giving highly acceptable reproduced images even in the long-time mode. Since the long-time mode is advantageous in terms of efficient use of the magnetic tape, the long-time mode has come to be more frequently used. Meanwhile, the broadcasting programs have a great variety to stimulate a desire for recording a plurality of programs within one and the same time zone. At present, recording two different programs within one and the same time zone or within overlapping time zones necessitates the use of two VTRs.
Further, video signals have come to be allowed to have a higher degree of definition by high-definition cameras which are called high vision cameras and serve as high-definition television signal sources. However, there is no apparatus that is capable of recording or reproducing any high-definition television signal that is other than the signal of the NTSC system.
Meanwhile, it has been known to obtain a stereoscopic vision by allowing each of reproduced images of two channels to be observed only by corresponding one of the eyes of the observer. In this instance, the signals of two channels must be simultaneously recorded. Then, since the amount of image data must be divided into 1/2, it has been practiced to thin out the signal of each channel for every other field.
In case that an ordinary image is to be ,reproduced from a recording medium on which a stereoscopic image signal is recorded in the above stated manner, the thinned out field portion of the signal in one of the channels has been interpolated to retain an adequate image quality as the signal of one of the channels is thinned out to have the vertical resolution thereof lowered to 1/2.
However, since the vertical resolution of the observable stereoscopic image is reduced to 1/2, the frame frequency is also reduced to 1/2. Therefore, the image reproduced in this manner in accordance with the conventional arrangement has a lower image quality with more flicker than ordinary images and thus causes a great visual fatigue when observed over a long period of time.